Methods for synthesizing carbon nanotubes on a substrate have been the subject of many applications in the prior art by means of the chemical vapor deposition technique (known under the abbreviation CVD for “Chemical Vapor Deposition”), based on decomposition of a carbon source (or a carbon precursor), for example a gas source (such as ethylene, acetylene) or a liquid source (such as toluene, ethanol) in the presence of a metal catalyst, the growing of carbon nanotubes on the substrate requiring a preliminary treatment of the substrate so as to improve interfacial adhesion between the substrate and the nanotubes.
The preliminary treatment of the substrate may consist in a heat treatment under suitable conditions.
Thus, document [1] (Thostenson et al., Journal of Applied Physics, Volume 91, Number 9, 2002, p. 6034-6037) describes a method for growing carbon nanotubes on a carbon fiber substrate respectively comprising a step for preliminary treatment of the substrate by heating the latter to 700° C. in vacuo, a step for depositing on this substrate a catalyst layer by magnetron spraying and finally a step for growing carbon nanotubes by the passing of an acetylene C2H2 stream.
Other authors have treated the substrate with chemical methods before growing carbon nanotubes.
Thus, document [2] (Sager et al., Composites Science and Technology 69 (2009), p. 898-904) describes, inter alia, a method for growing carbon nanotubes on a carbon fiber substrate, in which the substrate is treated with an alcoholic solution comprising magnesium sulphate MgSO4, before the passing of a flow comprising a carbon source (xylene) and a catalyst source (ferrocene) at 800° C. for 30 minutes.
Document [3] (Qian et al., Chem. Mater. 2008, 20, p. 1862-1869), as for it, proposes the growing of carbon nanotubes on a carbon fiber substrate, which has been treated beforehand by subjecting it to acid oxidation for 5 hours (with a 65% nitric acid HNO3 solution) followed by a basic washing (with 0.05M soda NaOH) for 24 hours.
Finally, the authors of document [4] (FR 2927619) before growing the carbon nanotubes on a fibrous substrate proceeded with depositing a ceramic sub-layer on said substrate, always with the idea of improving interfacial adhesion between the substrate and the carbon nanotubes and growth of the latter.
Thus, from most modes of application of the prior art, the requirement for proceeding with a surface treatment of the substrate emerges notably, when said substrate consists in carbon fibers, before proceeding with the growing on the latter of carbon nanotubes by chemical vapor deposition.
The inventors therefore set the goal of proposing a method for elaborating carbon nanotubes on a substrate without having to resort to a step for surface treatment of said substrate before growing said nanotubes, as this is the case of the applications of the prior art.